Pultruded part reinforced by longitudinal and transverse fibers and a method of manufacturing thereof

ABSTRACT

A method for forming a pultruded part includes collating reinforcing fibers by providing a first layer of reinforcing rovings extending in the longitudinal pultrusion direction, applying onto the first layer an intermediate layer of reinforcing fibers at least some of which include at least portions thereof which extend in the transverse direction and covering the intermediate layer with a second layer of rovings extending in the longitudinal direction. To the collated fibers is applied a resin so as to permeate through the layers and the materials are passed through a die to set the resin. The first and second layers are arranged to form first and second opposed surfaces of the part with the intermediate layer therebetween. The resin is a two part urethane resin which has sufficient strength to prevent the fibers from the first and second layers at the first and second surfaces respectively from breaking through the surface on bending of the wall thus allowing the use of the rovings at the surfaces with the transverse fibers therebetween so that the transverse fibers can be formed from loose or chopped fiber material from rovings rather than more expensive mat.

[0001] This application claims priority under 35 U.S.C.119 from aprovisional application initially given Ser. No. 09/880,087 filed Jun.14^(th) 2001 and now converted to provisional application Serial No.60/325,785.

[0002] This invention relates to a pultruded part reinforced bylongitudinal and transverse fibers and a method of manufacturing thepart.

BACKGROUND OF THE INVENTION

[0003] Pultrusion is a technique in which longitudinally continuousfibrous structures are used to pull a resin through a die so that theresin sets and produces a rigid part downstream of the die to which thepulling force is applied.

[0004] Originally the longitudinal fibres consisted of simplylongitudinal in the extending rovings and the parts were of a relativelysimple cross section such as rods, T-bars and the like. Howeverdevelopments have introduced to reduce the wall thickness of the partsso that complex cross sections including hollow cross sections could bemanufactured. In order to achieve the necessary strength of the parts,it was necessary to introduce transverse fibers to provide strength inthe transverse direction. Such transverse fibers are conventionallyapplied using a mat of a woven or non woven material. In many cases thefibers in the mat are generally random so that the number of fibersextending in the transverse direction is relatively small. One majorproblem with the mat is that it is relatively expensive and can be veryexpensive so that it is more than double per pound of the cost of thesimple conventional rovings. One direction of development has been toprovide improved mats which apply more of the fibers in the transversedirection thus allowing the mat to be of reduced thickness to providethe required strength or toughness in the finished part. An example of amat tailored for pultrusion is shown in published Internationalapplication PCT/WO78529A1 published Dec. 28, 2000 and assigned to Pella.

[0005] An alternative approach to the expense of the mat is to attemptto attach to the longitudinal rovings some transverse fibers which aresimply chopped roving material. On example of an arrangement of thistype is shown in U.S. Pat. No. 5,324,377 of the present inventor. Thismethod of pultrusion attempted to attach transverse fibers to theoutside of a body of longitudinal rovings so as to be carried throughthe die with the rovings. This method has to date not achievedcommercial success.

[0006] In order to minimize material costs, commercial pultrusion isnormally carried out using polyester as the resin which is a simplethermo-set resin material so that it can be applied to the fibers from abath and is thermo-set within the heated die. However polyester is alinear polymer which is thus not cross-linked so that it is relativelybrittle so that it tends to crack when bending forces are applied to thepart. This cracking is reduced by providing in the reinforcing fibers amat material at the surface of the wall of the part so that the fibersare held in place by the transverse fibers. This avoids or reduces thetendency of the longitudinal fibers to break through the surface of thepart on bending of the part. Up till now, therefore, polyester resinparts have required that the mat be applied on the outside surface. Thusin a hollow cross section, a mat is applied on the surface of each wallof the part so that there is a mat on the outside and also a mat on theinside surface with the normal longitudinal fibers being placed inbetween the two mats. This construction significantly increases the costof the part in that the mat is relatively expensive and two mats arerequired. Also the provision of two mats increases the thickness of thepart and thus again increases material costs.

[0007] Non-linear resins which may be cross-linked or amorphous such asepoxy have been available for some years and are used in pultrusion; butthese are significantly more expensive than polyester and thus have notachieved significant market penetration in conventional simple parts forwhich pultrusion is ideally suited.

[0008] Recently, improved non-linear resin materials particularly thosebased on urethane have become available which are still more expensivethan polyester but are not as expensive as other cross-linked resinssuch as epoxy. These cross-linked urethane resins could simply be usedin replacement for the conventional polyester which might lead toincreased strength where required or desirable. However and in mostcases the resins are of increased cost so it is necessary to considerthe possibility of otherwise reducing material costs to maintain acompetitive economic product while at least matching the strength of thecompetitive polyester product.

SUMMARY OF THE INVENTION

[0009] It is one object of the present invention, therefore, to providean improved pultruded part.

[0010] According to a first aspect of the invention, therefore, there isprovided a pultruded part comprising:

[0011] a wall having a first surface and a second surface spaced by athickness of the part, the wall extending longitudinally in a pultrusiondirection and having a transverse width transverse to the longitudinalpultrusion direction;

[0012] reinforcing fibers within the wall;

[0013] a non-linear resin material, which may be preferably cross-linkedor amorphous, permeated through the fibers and filling the thicknessbetween the surfaces so as to define the surfaces;

[0014] the reinforcing fibers including a first layer of fibersextending in the longitudinal pultrusion direction and located at thefirst surface;

[0015] the reinforcing fibers including a second layer of fibersextending in the longitudinal pultrusion direction and located at thesecond surface;

[0016] the reinforcing fibers including an intermediate layer of fibersat least some of which include at least portions thereof which extend inthe transverse direction and located between the first and secondlayers;

[0017] According to a second aspect there is provided a pultruded partcomprising:

[0018] a wall having a first surface and a second surface spaced by athickness of the part, the wall extending longitudinally in a pultrusiondirection and having a transverse width transverse to the longitudinalpultrusion direction;

[0019] the wall defining a peripheral wall fully surrounding a hollowinterior such that the first surface faces outwardly and the secondsurface faces inwardly;

[0020] reinforcing fibers within the wall;

[0021] a non-linear resin material, which may be preferably cross-linkedor amorphous, permeated through the fibers and filling the thicknessbetween the surfaces so as to define the surfaces;

[0022] the reinforcing fibers including a first layer of fibersextending in the longitudinal pultrusion direction and located at thefirst surface;

[0023] the reinforcing fibers including a transverse layer of fibers atleast some of which include at least portions thereof which extend inthe transverse direction and located at the second surface.

[0024] Preferably the resin is a urethane resin although other resinscan be used provided they cross-link which allows the fibers to belocated at the surface without the fibers cracking through the surface.

[0025] Preferably the resin is a two part material set by catalyticaction and is thermo-set. However other resins can also be used

[0026] In one arrangement, the fibers of the intermediate layer formfibers of a pre-formed mat which may be of a conventional constructiondefined by random continuous fibers boded or needle punched forconnection. The mat may also be of the construction shown in the abovepublished International Application assigned to Pella Corporation and onwhich the present inventor is one of the named inventors.

[0027] In another arrangement, the intermediate layer of fiberscomprises a plurality of cut fibers which are unsupported by mat fibersand are applied onto the second layer of fibers to be carried thereby.In this arrangement, the intermediate layer of fibers preferably consistwholly cut fibers.

[0028] Preferably the intermediate layer of fibers comprises primarilyand preferably wholly straight fibers extending transverse to thelongitudinal direction fully across the width of the part from one sideto the other side.

[0029] Preferably the reinforcing fibers consist only of the firstlayer, the second layer and the intermediate layer.

[0030] Preferably the transverse layer has a weight of less than 1oz/square foot preferably less than 0.5 oz/square foot. and morepreferably less than 0.25 oz/square foot since it has been found thatthe provision of increased amounts of fiber can interfere with thecross-linking of the resin and thus provide a decreased strength ratherthan the increase which would normally be expected with conventionalresins.

[0031] For this same reason, the transverse layer may be a scrim or meshhaving openings for penetration of the resin between the fibers so as toallow effective cross-linking of the resin. It has also been found thatsurprisingly a veil of staple polyester fibers having a weight of as lowas 0.1 oz/square foot can provide the required additional strengthand/or toughness to the product.

[0032] The transverse or intermediate layer may be formed of anysuitable fibers including but not limited to glass fibers, carbon fiberspolymer fibers such as polyester or aramids, metal strands such asaluminum or steel or natural fibers such as cotton, jute, hemp or flax.

[0033] Natural fibers such as flax have the advantage that they areinexpensive and are to some extent porous thus allowing the resin toenter the interstices in the fibers and providing an increased bondbetween the fibers and the resin which can lead to reduced de-laminationand thus increased strength.

[0034] Metal strands have the advantage that they provide the requiredadditional strength and/or toughness in the intermediate layer, but alsothey can provide other functions such as the required ferromagneticeffect for magnetic coupling as shown for example in U.S. Pat. No.5,129,184 (Fish) issued Jul. 14, 1992 and/or an electrostatic chargingeffect for electrostatic deposition of a coating or paint material.

[0035] In view of this increased strength in the resin, the wall mayinclude a leg portion thereof in which the reinforcing fibers consistsolely of the longitudinal fibers, that is there is no transversefibers. This is effected where the leg such as a glazing leg of a windowprofile has a length greater than 0.5 inches which would normallyrequire transverse reinforcement but a length less than about 1.0 incheswhere there is insufficient bending moment in the leg itself to allowcracking in the leg to occur. It will be appreciated that in anon-homogeneous material such as the pultrusions defined above thebending effect at an angle is different from that within a span of thematerial. Thus the provision of transverse fibers within a leg or spanof greater than 1.0 inches in length is required while such fibers arenot necessary at an angle between two legs of shorter length.

[0036] The leg portion may have a wall that is thicker than that of themain body portion; but this is provided for balancing of forces in thepultrusion process rather than in order to provide increased strength tocompensate for the absence of the mat or transverse fibers.

[0037] In one example such as for fenestration products, the main bodyportion defines a hollow section and the leg portion, generally aglazing leg, extends from one end at the hollow section to an opposedfree end.

[0038] The urethane resin used preferably in the embodiments describedhereinafter has the advantage that it is more resistant to degradationby UV and weather so that it is more suitable for fenestration products.

[0039] The construction described in the embodiments hereinafter alsomay have the advantage that it allows a reduced wall thickness. The use,in lower strength products such as fenestration products, conventionallyof two outside perimeter mats can be reduced by one mat to one mat sothat the total thickness can be reduced by at least 0.015 inch, which isthe typical thickness of one mat. In addition the increased strength inthe resin itself may allow a further reduction so that typically aconventional range in inches of polyester resin construction of 0.070 to0.180 for different end uses can be reduced to a range of 0.030 to0.120. A thickness even as low as 0.025 may also be possible forproducts such as fenestration products which require lower structuralstrength and a thickness of the order of 0.080 may be possible forproducts such as ladder rails or tool handles which require higherstructural strength. In particular the higher strength structuralproducts often include a third mat along the center and thus the threemats of the conventional product can be reduced to one mat or veil inthe arrangement described above thus yet further reducing the thickness.This reduction in mat content also increases the proportion oflongitudinal fibers or rovings and this also has the advantage that thelongitudinal stiffness of the part as provided by the longitudinalfibers is also increased. Thus a ladder rail may be reduced typically inthickness from 0.125 to 0.105 inch with an increase in strength.

[0040] In one advantageous arrangement, the transverse fibers are formedof metal strands which provide both transverse strength and thecharacteristic of electrical conductivity and/or ferromagnetism for thepart.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Embodiments of the invention will now be described in conjunctionwith the accompanying drawings, in which:

[0042]FIG. 1 is a cross sectional view of typical pultruded partaccording to to the present invention.

[0043]FIG. 2 is a cross sectional view on an enlarged scale of one wallof the part of FIG. 1, the cross section being at right angles to thatof FIG. 1.

[0044]FIG. 3 is a cross sectional view on an enlarged scale of one wallof the part of FIG. 1.

[0045]FIG. 4 is a schematic side elevational view of a method accordingto the present invention for manufacturing the part of FIG. 1.

[0046]FIG. 5 is a top plan view of the method of FIG. 4.

[0047]FIG. 6 is a top plan view of an alternative arrangement of theintermediate layer of the method of FIG. 4.

[0048]FIG. 7 is a cross sectional view on an enlarged scale of analternative construction of the fiber reinforcement used in the partshown in FIG. 1.

[0049]FIG. 8 is a first graph showing the comparative strength andmodulus of a series of coupon samples as set out in table 1 based uponstandard test ASTM D790.

[0050]FIG. 9 is a second graph showing the comparative strength of aseries of angle samples as set out in table 1 with the test beingentitled modified Lip Test.

[0051]FIG. 10 is a second graph showing the comparative strength of aseries of angle samples as set out in table 2 with the test beingentitled modified Lip Test 2.

[0052] In the drawings like characters of reference indicatecorresponding parts in the different figures.

BRIEF DESCRIPTION OF THE TABLES

[0053] Table 1 is a list of the materials tested in FIGS. 8 and 9.

DETAILED DESCRIPTION

[0054] In FIG. 1 is shown a typical cross section of a pultruded partwhich includes a hollow section 10, a leg 11 and a projecting portion12. The hollow section 10 includes four wails 10A, 10B, 10C and 10D eachof which has a thickness between an outer surface 10E and an innersurface 10F. Thus each wall part of the pultrusion must be manufacturedin a manner which provides the necessary strength to prevent cracking ofthe part.

[0055] In FIGS. 2 and 3 is shown a cross section of one wall of the partwhich is cut to form an end face 13. These cross sections show that thewall of the part is formed from a resin 14 which is shaped to define thesurfaces 10E and 1OF and a volume of the part is defined by a resinmaterial 15 which is interspersed between or permeated through fiberreinforcement 15 within the part. In the arrangement as shown, the fiberreinforcement includes a first layer 16 of longitudinally extendingfibers, primarily rovings, a second layer 17 also of longitudinallyextending rovings and an intermediate layer 18 of fibers arranged toprovide transverse strength.

[0056] The resin which extends through the part so that it defines thetwo surfaces of the part is a urethane resin available from ResinSystems Inc. of Edmonton, Alberta and is defined by a two-part resinwhich includes a catalyst for activating the resin. The particularlypreferred resin is known as Version G available from the above companywhich has the following characteristics:

[0057] 1. Version G provides an ideal VOC free high performancetwo-component polyurethane system for use in composite manufacturing.Version G exhibits physical properties that meet or exceed those ofexisting products—whether commodity polyesters, or specialty resins.

[0058] 2. Version G resin system is a general purpose thermosettingresin designed specifically for the composites pultrusion process.Version G is based on urethane chemistry, has been shown to provideexcellent composite properties, including superior toughness, shearstrength and resistance to cracking.

[0059] 3. Version G resin system is formulated to be a directreplacement for existing polyester or epoxy resins. In most cases, theexisting pultrusion dies, heaters and control systems can be used withrelevant minor modification for optimisation of processing. Version Gshows excellent physical properties when used with glass fiber sizing ofthe “polyester and vinyl ester ” type.

[0060] 4. Version G is a two-component resin that must be used with aresin injection system. The resin components may be mixed in a suitableratio, for example 1:1, by a standard static mixer placed prior to theinjection port. For dies not currently equipped for injection, a simpleinjection chamber, made from for example UHMW PE, material may be addedto the entrance end of the die. The resin system has been shown to workwith both high pressure and low pressure injection systems.

[0061] 5. Version G may be used directly as a “neat” system, or it maybe provided with fillers for cost reduction or property enhancement. TheVersion G may work with a recycled rubber crumb filler system, whichcombines synergistically with the urethanes to enhance toughness andcrack resistance properties or may use a more conventional calciumcarbonate filler material.

Key Benefits

[0062] Zero VOC's

[0063] Excellent impact resistance.

[0064] Thick section curing stability.

[0065] Lower operating temperatures.

[0066] Faster pulling speeds from higher reactivity.

[0067] Suitable for a wide variety of closed mold processes.

[0068] Secondary “processability”—Version composites readily acceptconstruction fasteners, or can be “punched” without any crazing orcracking.

[0069] In FIGS. 4 and 5 is shown schematically a method for using theresin for application to the reinforcing fibers to form the part of FIG.1.

[0070] Thus the longitudinal fibers 16 are supplied from roving bobbins16A to define a layer of the rovings arranged substantially side by sidewhich are carried forwardly through the pre-shaper 20 and the resininjection system 21 into the die 22 by a pulling system schematicallyindicated at 23 downstream of the die. As the layer 16 forms a band, itcan act as a conveyor carrying fibers forming the intermediate layer 18into the same elements for forming the pultruded part. The intermediatelayer 18 is covered by the upper layer 17 again formed from rovingssupplied from roving bobbins 17A thus the intermediate fibers areprotected and encapsulated as they are carried into the pultrusionsystem between the two layers 16 and 17. The pre-shaper 20 can thereforebe of a simple construction which causes the band defined by the threelayers to be shaped into the required shape to enter into the die toform the construction shown in cross section in FIG. 1. The constructionof the pre-shaper will be well known to one skilled in the art andtherefore does not require detailed explanation here.

[0071] The resin injection arrangement is designed for use with thetwo-part Version G resin material described above and therefore thereare two supplies supply 1 and supply 2 which are pumped from a containervia two separate pumps into a mixer immediately upstream of the resininjection system. The materials are therefore mixed for only a shortperiod of time before the resin is injected into the dry fibers so as topermeate through the fibers and to be carried by the fibers into thedie. The details of the mixer valve and the resin injection system areagain well known to one skilled in the art and provide the necessarycontrols for varying the mix proportions and for ensuring that therequired amount of resin is maintained within the injection system.

[0072] In view of the fact that the transverse fiber layer 18 isprotected within in the two layers 16 and 17, it is possible to supplythe transverse fiber layer either as a pre-formed mat or as individualchopped fibers. Pre-form mat is relatively expensive since it involvesan additional process and this may double or triple the base materialcosts. In FIG. 5 therefore is shown a cut fiber supply device 25 whichreceives fibers from yarn or roving supplies 26 and chops those fibersinto fiber strands 27 laid across the width of the layer 16 defined bythe rovings 16A. These fibers can thus be laid loosely across the layer16 since they will be covered by the layer 17 supplied from the rovings17A at a guide roller R. In a yet further arrangement, the fibers of theintermediate layer can be added by mixing cut fibers with the resinmaterial and injecting the resin between the roving layers so that theresin permeates through the roving layers while leaving the cut fibersbetween the rovings. Such cut fibers can be introduced to the resinduring the mixing stage and can pass through the pump with the resininto the die block as described herein.

[0073] As the rovings carry the cut fibers, or other fibers of theintermediate layer however they are introduced, there is no problem ofthe intermediate layer skewing as it enters the die and no requirementtherefore for anti-skewing arrangements within the intermediate layer.It will be appreciated that the application of cut fibers hassignificantly less structural stability than even the thin mats andveils described herein and yet even these cut fibers can be introducedwithout skewing or other breakdown of the layer becoming a problem.

[0074] The intention is therefore to provide fibers which extend withtheir direction primarily or wholly across the width of the layer 16 soas to avoid the necessity for additional fiber elements within the layer18 which do not contribute to the transfer strength. The supply element25 therefore forms in effect a gun which fires the fibers onto the layer16 but without sufficient force to disturb the layer 16. Conventionalchopping guns can be used for this purpose or a gun can be designedwhich fires the fibers across the width of the layer 16 so that they arecut only when they reach across the full width thus laying them acrossthe full width as shown in FIG. 5.

[0075] In an alternative arrangement, the intermediate layer is formedsimply from a mat pre-formed using conventional materials.

[0076] The fibers of the intermediate layer can be formed from glassusing relatively thick or coarse fibers for strength or can be fineglass fibers of the type normally formed to provide a veil. The coarsefibers would normally have a weight less than 1 ounce per square foot.Other such mats may have a weight of the order of 0.5 ounces per squarefoot. The lightweight veil material formed of fine glass fibersgenerally has a weight of the order of 0.25 ounces per square foot.

[0077] An alternative material which can be used is a polyester veilmaterial which is formed by staple fibers of fine polyester in a matwhich can be heat bonded using high and low melt fibers in the polyestermat. Such a mat may have a weight of the order of 30 grams per squaremeter which is equal to 0.1 ounces per square foot approximately.

[0078] In FIG. 8 is shown a graph of the results from a first series ofdifferent trials of materials 1 to 8 shown in table 1. The results arebased upon a standard ASTM coupon test identified as ASTM D790:

[0079] In FIG. 9 is shown a table of results from a second series ofdifferent trials of the same materials from table 1. The results arebased upon test of right angle pieces formed from the materials set outin Table 1 where the strength to break was determined by bending theangle piece in a direction to increase the angle from the nominal 90degrees to breaking of the part. It will be noted that materials 9 and10 in Table 1 were not used in the tests of FIG. 8.

[0080] In FIG. 10 is shown a table of results from a series of trials ofthe materials from identified at the bottom of the figure. The resultsare based upon test of right angle pieces where the strength to breakwas determined by bending the angle piece in a direction to increase theangle from the nominal 90 degrees to breaking of the part. Forexplanation of the figure it will be noted that the items marked“polyester” are of a conventional nature using the conventional resin.Those marked “RSI” use the resin of the present invention. Where apercentage is given, this relates to the percentage of filler material.“920” “Nico” and “OCF” all relate to particularly types of mat asexplained hereinbefore. The terms “blue”, “green” and “yellow” relate toconventional ladder rail material known by those in the art to relate toparticular grades of the material for required strengths. It is theseconventional strengths which the present invention is attempting tomatch and it will be noted that these are exceeded for example by thesamples “RSI/poly veil/15%” and “RSI/poly veil/0%” which areparticularly preferred in this invention. Such examples can exceed thestrength requirement while manufacturing at reduced cost with a thinnerpart and of increased longitudinal stiffness.

[0081] The conclusions from the above trials are that the urethane resinof RSI in the absence of transverse fibers does not have sufficientstrength or toughness in wall widths greater than of the order of 1.0inches to match the required strengths for the required parts. It isnecessary therefore to add the transverse fibers when the wall width isgreater than of the order of 1.0 inch in order to provide this necessarystrength or toughness. When the height of for example the leg 11 asshown in FIG. 7 has a height no greater than of the order of 1.0 inches,the strength of the resin alone in conjunction with solely thelongitudinal fibers is sufficient to provide the required strength ortoughness for the leg to prevent cracking of the leg within its width orat the angle joint with the remainder of the part. When the wall widthsuch as the walls 10A and 10B in FIG. 7 have a greater width which canbe as much as 2 to 3 inches, it is necessary to provide the transversefibers to provide the necessary strength against fracturing duringbowing of the wall. The thickness of the leg may increased so that it isat least 10% thicker and may be as much as approximately double thethickness of the walls 10A and 10B.

[0082] The increase in thickness of this range will still allow the partto be pultruded through the die without significantly imbalancing thefiber structure as it enters the die and passes through the die. It willbe appreciated in this regard that the mandrel necessary to form thehollow interior is floating so that it is necessary to balance thefiberous structure so the mandrel floats in the required position anddoes not deviate to one side which would significantly reduce thethickness of the wall at that one side. In order therefore to maintainthe walls 10A, 10B, 10C and 10D approximately the same thickness, someincrease in the thickness of the leg 11 can be accommodated but notgreater than the value set forth above.

[0083] It is yet further concluded from the above results that somewhatsurprisingly an increase in the amount of transverse fibers does notlead to an increase in the transverse strength. It is believed that thisoccurs due to the fact that the presence of the transverse fibersinhibits the formation of cross linking within the resin so that thepresence of the fibers does not make up for the absence of crosslinking. Thus the structure can de-laminate under inter-laminar shear atthe transverse fibers when bending particularly at a junction forexample between the leg 11 and the wall 10A. Thus the arrangement of thepresent invention preferably uses a minimum quantity of transversefibers which are necessary to provide for the resin the increase instrength for the walls 10A and 10B to match conventional strengths. Thisreduces the tendency to de-laminate under inter-laminar shear whichcould otherwise occur where thicker layers of transverse fibers or matsand used.

[0084] In FIG. 7 it will also be noted that the mat layer indicated at18N is located on the inside surface of each of the walls 10A, 10B, etc.Thus the mat forms the innermost layer and the remainder of the wall isreinforced by the conventional longitudinal fibers indicated at 17N.

[0085] Conventionally it is problematic for a pultrusion to pass throughthe die where the components are not balanced. Thus where the mat isprovided only at one surface, this is normally not acceptable since thisprovides different levels of drag against the different sides of the diewhich imbalance the structure and tend to generate bowing or distortionin the product. However in this case it is possible to run a hollowstructure where the mat is wholly on the inside surface and only in thehollow section, since this allows a suitable balancing of the structurewhile maintaining the wall thicknesses substantially equal and constant.The use of a single mat reduces material costs. The single mat can bevery thin and very light since it is required merely to provide slightlyadditional transverse strength for the cross linked resin. The absenceof a mat in the outside surface of the part can provide an improvedquality of appearance in the outside surface.

[0086] The absence of the mat at the junction between the leg 11 and thewall 10A reduces the risk of de-lamination in the event that the leg 11is twisted by forces applying a pivotal action about a pivot axis at thebottom of the leg 11. Thus the absence of any de-lamination at thispoint allows the resin to provide its natural cross link strength toprevent cracking at that location. Cracking along the wall 10A isprevented by the cross linking of the resin and by the presence of themat 18N.

[0087] Since various modifications can be made in my invention as hereinabove described, and many apparently widely different embodiments ofsame made within the spirit and scope of the claims without departingfrom such spirit and scope, it is intended that all matter contained inthe accompanying specification shall be interpreted as illustrative onlyand not in a limiting sense. TABLE 1 1 OCF mat, Polyester resin, regularprocess 2 Nico mat, Polyester resin, regular process 3 No mat - allroving, RSI resin 4 Fibermesh, RSI resin, Roving-mat-roving matrix 5Nico mat, RSI resin, Roving-mat-roving matrix 6 OCF mat, RSI resin,Roving-mat-roving matrix 7 Polyester veil, RSI resin, Roving-mat-rovingmatrix 8 Omnimat, RSI resin, Roving-mat-roving matrix 9 Aluminum mesh,RSI resin, Roving-mat-roving matrix 10 Steel mesh, RSI resin,Roving-mat-roving matrix

[0088]

We claim:
 1. A pultruded part comprising: a wall having a first surfaceand a second surface spaced by a thickness of the part, the wallextending longitudinally in a pultrusion direction and having atransverse width transverse to the longitudinal pultrusion direction;reinforcing fibers within the wall; a non-linear resin materialpermeated through the fibers and filling the thickness between thesurfaces so as to define the surfaces; the reinforcing fibers includinga first layer of fibers extending in the longitudinal pultrusiondirection and located at the first surface; the reinforcing fibersincluding a second layer of fibers extending in the longitudinalpultrusion direction and located at the second surface; the reinforcingfibers including an intermediate layer of fibers at least some of whichinclude at least portions thereof which extend in the transversedirection and located between the first and second layers.
 2. Apultruded part comprising: a wall having a first surface and a secondsurface spaced by a thickness of the part, the wall extendinglongitudinally in a pultrusion direction and having a transverse widthtransverse to the longitudinal pultrusion direction; the wall defining aperipheral wall fully surrounding a hollow interior such that the firstsurface faces outwardly and the second surface faces inwardly;reinforcing fibers within the wall; a non-linear resin materialpermeated through the fibers and filling the thickness between thesurfaces so as to define the surfaces; the reinforcing fibers includinga first layer of fibers extending in the longitudinal pultrusiondirection and located at the first surface; the reinforcing fibersincluding a layer of fibers at least some of which include at leastportions thereof which extend in the transverse direction and located atthe second surface.
 3. The pultruded part according to claim 1 whereinthe resin is a cross-linked resin.
 4. The pultruded part according toclaim 1 wherein the resin is a urethane resin.
 5. The pultruded partaccording to claim 4 wherein the resin is a two part material set bycatalytic action.
 6. The pultruded part according to claim 4 wherein theresin is thermo-set.
 7. The pultruded part according to claim 1 whereinthe transverse layer of fibers comprises a mat.
 8. The pultruded partaccording to claim 1 wherein the transverse layer of fibers comprises aplurality of cut fibers.
 9. The pultruded part according to claim 1wherein the transverse layer of fibers comprises wholly cut fibers. 10.The pultruded part according to claim 1 wherein the transverse layer offibers comprises primarily fibers extending transverse to thelongitudinal direction.
 11. The pultruded part according to claim 1wherein the transverse layer of fibers comprises wholly fibers extendingtransverse to the longitudinal direction.
 12. The pultruded partaccording to claim 1 wherein at least some of the fibers of thetransverse layer of fibers are substantially straight and extend fullyacross the width of the part from one side to the other side.
 13. Thepultruded part according to claim 1 wherein the reinforcing fibersconsist only of the first layer, the second layer and the transverselayer.
 14. The pultruded part according to claim 1 wherein thetransverse layer has a weight of less than 1 oz/square foot preferablyless than 0.5 oz/square foot and more preferably less than 0.25oz/square foot.
 15. The pultruded part according to claim 1 wherein thetransverse layer is a scrim or mesh having openings for penetration ofthe resin between the fibers.
 16. The pultruded part according to claim1 wherein the transverse layer is formed of glass or polymer fibers ormetal strands.
 17. The pultruded part according to claim 1 wherein thewall includes a leg portion thereof in which the reinforcing fibersconsist solely of the longitudinal fibers.
 18. The pultruded partaccording to claim 17 wherein the leg portion is connected to a mainbody portion only at one end so as to define a second free end.
 19. Thepultruded part according to claim 17 wherein the leg portion has a wallthat is thicker than that of the main body portion.
 20. The pultrudedpart according to claim 17 wherein the main body portion defines ahollow section and the leg portion extends from one end at the hollowsection to an opposed free end.
 21. The pultruded part according toclaim 1 wherein the transverse fibers are formed of metal strands whichprovide both transverse strength and the characteristic of electricalconductivity and/or ferromagnetism for the part.